stare down the barrel of a (one's) gun イディオム
big gun/cheese/wheel/wig
an important person, a leader The new director was a big wheel in his previous company but is not so important now.
go great guns
do something very fast or very hard, successfully The workers were going great guns fixing the building when I saw them this morning.
going great guns
working very well, going strong We were going great guns till our goalie got hurt. Then they scored.
great guns
(See going great guns)
gun down
shoot, kill with guns He was gunned down as he left his apartment - shot in the back.
gun for someone
look hard for a chance to harm or defeat someone My supervisor has been gunning for me for a long time but I don
gun for something
try very hard to get (prize or promotion etc.) He has been gunning for the new sales job for a long time.
gun it
step on the accelerator, floor it, goose it When a car tried to pass him, he gunned it. He sped away!
gung-ho
enthusiastic, full of eagerness She is really gung-ho about her new job at the library.
jump the gun
act too soon, leave early A good chef waits until the food is cooked. Don't jump the gun.